It is common practice in the electrical industry to use terminal posts in circuit boards which posts have compliant mounting portions integral therewith. When a terminal post of this type is inserted into a hole in a circuit board, the mounting portion is deformed upon entry into the circuit board hole so that the mounting portion bears against the cylindrical surface of the hole thereby retaining the post in the circuit board. Most terminal posts having these compliant mounting portions are intended for use with circuit boards having plated through-holes, that is, holes having a metallic surface so that the terminal post will be placed in electrical contact with the plating when it is inserted into the hole. No subsequent soldering is required for posts of the compliant type. U.S. Pat. Nos. 4,186,982, 4,206,964 and 4,066,326 show typical terminal posts having compliant mounting portions.
Most of the terminal posts having compliant mounting portions which are presently available are formed from solid bar stock having a square cross-section and are made in standard sizes, usually 0.025" square or 0.045" square. The compliant mounting portions may be formed by shearing a blank and offsetting two portions thereof in a forming die in a manner such that these two portions are displaced towards each other when the post is inserted into a circuit board hole. Alternatively, the posts can be stamped from relatively thick metal stock, as shown in the above identified U.S. Pat. No. 4,206,964. It would be desirable under many circumstances to have terminal posts having compliant mounting portions which are formed of relatively thin sheet metal stock so that an additional terminal device, for example, a terminal socket, might be formed integrally with the terminal post. U.S. Pat. No. 3,420,087 discloses and claims a stamped and formed terminal device having resilient contact portions of relatively thin sheet metal and having an integral terminal post formed also from relatively thin sheet metal. The terminal post portion of the terminal devices shown in this prior art patent is produced by stamping and forming portions of a flat blank into a U-shaped cross-section and during these forming operations the blank is severely coldworked and hardened. The resulting post portion of the terminal is thus relatively stiff and has all of the characteristics of a solid post, while the remaining portion of the terminal has the characteristics of a stamped and formed sheet metal terminal device which may have resilient contact means, such as a contact socket or resilient spring arm thereon.
The present invention is directed to the achievement of a terminal post having a compliant mounting means integral therewith and is formed from relatively thin sheet metal. The present invention is thus directed to the achievement of a compliant mounting portion on a stamped and formed terminal post of the general type disclosed in the above identified U.S. Pat. No. 3,420,087.
The invention is further directed to the achievement of a terminal post having a compliant mounting portion which has elastic characteristics to the extent that a post can be extracted from a hole into which it has been inserted and reinserted at a later time without detrimental effects on the retaining power of the post or the electrical contact with the plating material in the hole. The invention is further directed to the achievement of a compliant post which can be produced for use in circuit board holes having a relatively wide range of diameters. The invention is also directed to the achievement of a terminal post having a compliant mounting portion which can be produced with varying characteristics as regards the force exerted by the compliant portion on the circuit board hole, the insertion and extraction forces and other variables.
Terminal posts in accordance with the invention can be produced by starting with a flat blank of conductive sheet metal, such as brass or beryllium copper, and first punching a slot in the blank at the desired location of the compliant portion of the finished post. A curved portion or arcuate portion, is then formed in the blank in the vicinity of the slot so that the material on each side of the slot is bowed outwardly from the plane of the blank. Thereafter, the stock material extending from the ends of the blank to the slot is formed into a U-shaped cross-section by forming methods which include severe coldworking of these portions of the blank during the U-ing operation. During the U-ing operation, the material on each side of the slot is swung through an angle of 90.degree. and the bowed portions thus become extensions of the sidewalls of the U-shaped portions of the post when it is formed to its final shape. The bowed portions of the blank are not subjected to the severe coldworking imposed on the remainder of the blank during the U-ing operation and these bowed portions thereby serve as resilient or elastic mounting portions which will deform towards each other when the post is inserted into a circuit board hole.